1. Field of the Invention
The present invention relates to post tension segmental construction. More particularly, the present invention the relates to deviators as used with external tensioning in segments in such segmental construction.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Precast segmental bridges are known and commonly used throughout the world as a means to forge roadways through mountainous terrain or across rivers or other barriers. Such bridges are typically constructed in accordance with the following sequence: First, a series of upright piers are formed along the bridge span. Thereafter, cantilevered bridge sections are built out of each pier by successively mounting the precast segments to previously completed bridge components and post-tensioning the segments thereto. The cantilevered bridge sections are built out from each pier in a symmetrical fashion so that the piers are not subjected to undue bending loads. When the cantilevered sections are complete, the ends thereof are post-tensioned together to form a continuous bridge deck. Typically, two such bridge spans are constructed to accommodate the two directions of travel. These spans are generally side-by-side, but need not be parallel (horizontally or vertically) nor at the same elevation.
FIGS. 1-4 illustrate a form of such precast segmental bridge construction in accordance with the teachings of U.S. Pat. No. 5,231,931, issued on Aug. 3, 1993 to G. Sauvagiot. This form of segmental precast bridge construction is particularly disclosed as used with a rapid transit viaduct system.
Referring to FIG. 1, there is shown an end view of a rapid transit viaduct section 2 with rapid transit vehicles 32 and 34 thereon. The section 2 includes a concrete segment 3. The section 2 has a central load-bearing member, or body member 4, supported by a pair of upright pier members 6 and 8. Extending laterally from opposite lower side portions of the body member 4 are a pair of lateral platform structures 10 and 12. Each of the platform structures 10 and 12 has a pair of rails 14 mounted thereon for carrying a rapid transit vehicle 32 and 34. In addition, each of the platform structures 10 and 12 can have an upright sidewall section 16 as required for safety, noise pollution, and other considerations. One or more sets of rails 14 are carried by each of the lateral platform structures depending on the requirements of the transit systems.
The platform structures 10 and 12 each include respective upper platform decks and respective lower support struts 22 and 24. The lower support struts 22 and 24 are mounted as close to the bottom of the body member 4 as practicable. Deck members 18 and 20 are mounted to the body member 4 at an intermediate portion thereof above the support struts 22 and 24. The support struts 22 and 24 angle upwardly from their point of attachment with the body member 4 until they intersect the deck members 18 and 20. As such, the deck members 18 and 20 and support struts 22 and 24 form a box section providing resistance to torsional loading caused by track curvature and differential train loading. This box section may be considered a closed base. The body member 4 bisects the closed base and extends vertically upwardly therefrom to provide span-wise bending resistance. Preferably, the entire duct section 2 is cast as a single reinforced concrete cross-section.
The platform structures 10 and 12 each include lower pier mounts 26 and 28. These are mounted respectively to the bottom of the support structures 22 and 24. The pier mounts 26 and 28 are, in turn, supported, respectively, on the piers 6 and 8 using a plurality of neoprene pads 30, which provide a cushioned support for the structure.
The viaduct section 2 shown in FIG. 1 forms part of a viaduct system supporting rails 14 for carrying rapid transit vehicles 32 and 34. The viaduct section 2 may be formed as a precast modular segment 3. The viaduct section 2 is then combined with other viaduct sections to form a precast segmental structure. To facilitate such construction, the body member 4 may be formed with interlock member 36, while the lateral platform structures 10 and 12 may be each formed with interlock members 38.
Referring to FIG. 2, there is shown a plan view of a viaduct system formed from precast sections 2. The sections 2 are modular concrete segments that are combined to form a precast segmental structure extending between sequentially positioned piers (not shown). The sections 2 are placed in longitudinally-abutting relationship. To facilitate that construction, the sections are match cast so that the abutting end portions thereof fit one another in an intimate interlocking relationship. Each successive section is therefor cast against a previously cast adjacent section to assure interface continuity.
The connection between adjacent modular sections 2 is further secured by way of the interlock members 36 and 38. On one end of each section 2, the interlock members 36 and 38 are formed as external key members. On the opposite end of each section 2, the interlock members are formed as an internal slot or notch, corresponding to the key members of the adjacent viaduct system. Matchcasting assures that corresponding key members and slots, as well as the remaining interface surfaces, properly fit one another.
As seen in FIG. 2, the sections 2 are bound together with one or more post-tensioning cables or tendons 40, 42 and 44. The number of cables used will depend on a number of factors such as cable thickness, span length, and loading requirements. The tensioning cables are each routed along a predetermined path which varies in vertical or lateral position along the span of the segmental structure. The tensioning cables are used for lateral tensioning and the external tensioning at the segments.
Referring to FIG. 3, there is shown an end view of a concrete segment 3 used in segmental construction of a rapid transit system. Adjacent segments are held together by post-tensioning cables 42 and 44 that extend through the concrete segment 3. As can be seen in FIG. 3, post-tensioning cables 40 are positioned externally of the concrete segment 3, and internal post-tensioning cables 42 and 44 are positioned internally of the concrete segment 3. Cables 42 and 44 extend through tunnels 50 formed in the concrete segment 3. It is important to note that multiple post-tension cables 42 can extend through a single tunnel 50 formed within the concrete segment 3. Cables 45 are shown as extending through the box 47 of the segment 3. Cables 45 are utilized for the external tensioning of the concrete segments. Experiments have shown that 50% internal tensioning and 50% external tensioning is optimal for such construction.
In such post-tension segmental construction, piers occur periodically along the length of the structure. When these piers occur, it is necessary to use a generally solid concrete segment at the segment on top of the pier. Additionally, it is necessary to route the post-tension tendon in a proper direction through such a solid concrete segment. Typically, this will require that the tendons will have a bend extending through this segment and a bend extending outwardly of the segment. Typically, when the cables have a bend, they will bear very strongly against the ends of the duct through which they pass. This can establish an undesirable point-of-contact force. Ultimately, the forces that occur because of this abrupt point-of-contact could potentially damage the post-tension tendon after the tensioning has occurred or would damage the integrity of the duct through which such tendons pass. As such, a need has developed so as to provide a duct which minimizes the effect of the point-of-contact of the bend of the post-tension tendons with the surfaces of the duct. Additionally, there is a need to enhance the ability to properly route the post-tension tendons through the duct.
Various patents have issued, in the past, for devices relating to such multi-strand duct assemblies. For example, U.S. Design Pat. No. 400,670, issued on Nov. 3, 1998, to the present inventor, shows a design of a duct. This duct design includes a tubular body with a plurality of corrugations extending outwardly therefrom. This tubular duct is presently manufactured and sold by General Technologies, Inc. of Stafford, Tex., the licensee of the present inventor.
U.S. Pat. No. 5,762,300, issued on Jun. 9, 1998, to the present inventor, describes a tendon-receiving duct support apparatus. This duct support apparatus is used for supporting a tendon-receiving duct. This support apparatus includes a cradle for receiving an exterior surface of a duct therein and a clamp connected to the cradle and extending therebelow for attachment to an underlying object. The cradle is a generally U-shaped member having a length greater than a width of the underlying object received by the clamp. The cradle and the clamp are integrally formed together of a polymeric material. The underlying object to which the clamp is connected is a chair or a rebar.
U.S. Pat. No. 6,666,233, issued on Dec. 23, 2003 to the present inventor, shows another form of a tendon-receiving duct. In this duct, each of the corrugations is in spaced relationship to an adjacent corrugation. The tubular body has an interior passageway suitable for receiving cables therein. Each of the corrugations opens to the interior passageway. The tubular body has a first longitudinal channel extending between adjacent pairs of the corrugations on the top side of the tubular body. The tubular body has a pair of longitudinal channels extending between adjacent pairs of the corrugations on a bottom side of the tubular body.
U.S. Design Pat. No. D492,987, issued on Jul. 13, 2004, to the present inventor, illustrates a design of a three-channel duct having a plurality of generally trapezoidal-shaped ribs with a first channel extending across a top of the tubular body and a pair of channels extending across the bottom of the tubular body.
U.S. Design Pat. No. D492,988, issued on Jul. 13, 2004 to the present inventor, discloses a monostrand duct for receiving a single tendon therein. This monostrand duct has a plurality of ribs formed along the exterior of the body. Each of the ribs has a generally box-like cross-section. A pair of diametrically-opposed longitudinal channels extend along the length of the duct and between each of the ribs.
It is an object of the present invention to provide a deviator system that is light, corrosion-resistant and has superior bonding properties with concrete.
It is another object of the present invention to provide a deviator system that prevents concrete spalling and deterioration due to expansion of corroding elements.
It is another object of the present invention to provide a deviator system that can be easily placed into concrete segments.
It is another object of the present invention to provide a deviator system which reduces material costs.
It is a further object of the present invention to provide a deviator system which is easy to transport, easy to handle, and easy to install.
It is an other object of the present invention to provide a deviator system which facilitates the ability to establish 50% internal post-tensioning and 50% external post-tension in such segmental construction.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.